#include <stdio.h>
#include <string.h>
int main()
{
	double sum = 0.0;
    int flag = 1;
	for (int i = 1; i <= 100; i++)
	{
		sum = sum + 1.0*flag / i;
		flag = -flag;

	}
	printf("%lf", sum);
	return 0;
     
}